1. Field of the Invention
This application relates generally to roof ventilation systems, and specifically to ventilation systems for roofs employing solar panels.
2. Description of the Related Art
A roof of a building typically includes roof vents that ventilate the region directly underneath the roof, which is ordinarily the building's attic space. Ventilation of the attic is important in keeping the building temperature from rising to undesirable levels. A variety of different types of roof vents exist, such as field vents, eave vents, ridge vents, soffit or undereave vents, and the like. Of particular interest for the present application is a field vent, which is a vent positioned within the “field” of a roof, and which allows airflow through the roof field between regions above and below the roof.
For example, FIG. 1 shows a building 10 with a typical roof 11 comprising two fields 12 and 14 joined together at an upper ridge 16, the lower ends of the fields defining eaves 18 and 20. While FIG. 1 illustrates a very simple roof structure with only one linear ridge and only two roof fields, many buildings have more than two field portions and multiple linear ridge sections. The illustrated roof 11 includes a plurality of field vents 22, which allow airflow between the building's attic and the exterior atmosphere. Many different types of field vents 22 exist. Typically, field vents 22 are designed to permit airflow while preventing the ingress of snow, water, vermin, and debris into the building 10. Accordingly, field vents 22 may include screens or other types of filters, as well as baffles to prevent the ingress of wind-driven rain through the vent.
FIG. 2 shows a cross-sectional view of the roof 11. The roof 11 typically comprises a roof deck 24 secured over a frame structure 26, and a covering structure 28 overlaying the roof deck 24. The frame structure 26 normally comprises a plurality of rafters 30 (e.g., wooden beams) extending generally from the ridge 16 to the eaves 18 and 20. The roof deck 24 typically comprises a structural layer formed over the frame structure 26, such as plywood sheeting nailed onto the rafters 30. The covering structure 28 is provided as a shield against the elements, including solar radiation, rain, snow, and the like. Common covering structures include concrete and clay tiles, shingles, and so-called “composition roof sheets,” which are normally a composite of tar paper, recycled asphalt, and other materials provided on a felt underlay. In FIG. 2, the roof 11 comprises a tile roof. While the illustrated covering structure 28 comprises so-called “S-shape” tiles 32, many different shapes and sizes of tiles are employed in tile roofs. The tiles 32 typically rest upon battens 34 interposed between the tiles and the roof deck 24, the battens 34 oriented parallel to the ridge 16 and eaves 18 and 20. FIG. 3 shows a cross-sectional view of the roof 11 depicted in FIG. 2. In FIG. 3, the tiles 32 are illustrated as flat tiles instead of as S-shaped tiles.
Referring again to FIG. 1, some field vents 22 are designed to mimic the appearance of the roof 11, so that the vents blend in visually. For example, if the roof 11 comprises a tile roof, the field vents 22 can be designed to mimic the shape and color of the tiles. Exemplary vents are sold by O'Hagin's, Inc. of Sebastopol, Calif. Such vents typically include a subflashing member (also referred to as a primary vent member) that resides within an opening in the roof deck, and a secondary vent member positioned above the subflashing member. The subflashing member includes an opening that communicates with the opening in the roof deck. The secondary vent member is shaped like one of the tiles of the tile roof, and covers the openings in the subflashing member and the roof deck so as to prevent the ingress of snow, rain, etc. The secondary vent member typically includes one or more other openings to provide a path for airflow through the vent. In most field vents of this variety, there is no direct line of sight through the openings in the secondary vent member and the subflashing member. Typically, the vent members include louvers, screened openings, or other types of openings combined with baffles, spacers, diverters, or a combination thereof to prevent the ingress of water, wind-driven rain, vermin, and debris into the building while still permitting airflow through the openings of the subflashing member and the secondary vent member. Examples of such types of field vents are illustrated and described in U.S. Pat. Nos. 6,447,390 and 6,050,039, the full disclosures of which are hereby incorporated herein by reference.
Due to increasing energy costs, the use of solar panels provided on building roofs has increased in recent years. In one type of installation, a field of solar panels is provided on top of the covering structure 28 (e.g., on top of the roof's layer of shingles, tiles, composition shingles, steel sheets, or other roofing materials). In another installation, the solar panels form a portion of the covering structure 28, effectively replacing sections of shingles, tiles, or other roofing materials. In either case, the field of solar panels is typically supported by a grid structure provided on the roof. The solar panels convert solar radiation into electricity. The solar panels are normally wired through the roof to transmit this electricity to (1) one or more batteries associated with the building, (2) a community power grid (for which power customers can sometimes obtain discounts on their power bills), and/or (3) devices requiring electricity for operation.